In numerous fields of technology, it is often desirable, and sometimes necessary, to limit a moving part to straight line motion.
One particular application is in data storage systems. For example, with tape drives, the recording head moves back and forth across the width of the recording tape. Guiding the recording head in a linear path is critical to retrieving accurate information from storage tracks.
There are many known arrangements for guiding a movable part linearly. A common arrangement couples the moving part to parallel posts so that the moving part is constrained to a straight line path. The moving part is coupled to parallel posts by brackets which surround the posts. In this design, free motion is achieved by designing the dimensions of the brackets so that their circumference is slightly larger than that of the posts. This clearance enables the moving part to freely move along the posts.
However, this clearance between the bracket and posts, regardless of how slight it is, creates a looseness which often allows the moving part to tilt slightly while in motion. In some applications, particularly where accuracy is critical, this clearance may prohibit the retrieval of accurate data.
Another problem with the above arrangement is that friction results as the brackets coupled to the moving part move along the posts. Because the brackets must retain some closeness to the posts to enable the moving part to remain stationary when necessary, the moving part is prevented from moving smoothly along its direction of motion. Particularly where small motion increments are required, as with the retrieval of data from storage systems, friction can cause the retrieval of inaccurate information. Although there are antifriction linear bushings available, they still possess some friction and are fairly costly.
Other devices in the prior art attempt to approximate straight line motion by using linkages. There are inherent inaccuracies and clearances associated with these devices that cannot be tolerated when accuracy and speed are critical.
As capacities of storage systems increase, the use of a magnetic head guide which creates straight-line mechanical motion and has an improved accuracy when handling these higher capacities will be necessary.
The problem presented by the prior art is to provide an arrangement that guides a moving part in a straight line motion path, without the tilting of the part, or the creation of sliding friction as the part moves.